〈FIG 1〉The Annals of King Sejong Geographical Records (1454)
In The Collected Writings of Mogeun
by Yi Saek, a scholar and writer active in the fourteenth century, is the phrase, “The day is clear and so seasonable.” The expression “風日” means literally a windy day, but in this context the term can be interpreted as meaning weather. The expression “淸明” implies the clear, blue sky without any cloud. Since Yi Saek, the expression has been used by many to describe Korea’s clear autumn sky.
The same expression appears again in History of Goryeo Geographical Records in the fifteenth century: “Some say that Usan and Mureung were originally two islands that are not far apart, and each can be seen from the other when the weather is clear.” This corresponds to the expression in The Annals of King Sejong Geographical Records
also from the fifteenth century.> (FIG 1) The comment that the two islands in the East Sea (Ulleungdo and Dokdo) face each other is found here.
In Gazetteer of Joseon
; 與地圖書), which was printed in the eighteenth century, the same expression may be seen: “Ulleungdo, or alternatively called Ureungdo, is located in the southeast of the county.” The three peaks are high in the sky and South Peak is the lowest (“three peaks” can also be interpreted as meaning “the south peak of the three”). On clear days, the trees atop the peaks and the sand banks at the foot of the mountain top are clearly visible.
〈FIG 2〉 Comparison of Size of Ulleungdo and Dokdo
In the seventeenth century, there is a comment by Jang Han-sang in his Historical Records of Ulleungdo
that as an officer responsible for vacating Ulleungdo, he landed on the island and searched for non-complying residents between the nineteenth day of the ninth month and the third day of the tenth month in 1694 (twentieth year of King Sukjong). He wrote, “To the west, one can see the meandering Daegwan Pass, and there is an island in the middle of the sea to the east. Located in the east-southeast about 300 ri (117.8 kilometers) away, the island is one-third of Ulleungdo in size.” Measured today, Dokdo is about .3 percent of Ulleungdo’s size (FIG 2). Compared to the size of Jejudo, the biggest island in Korea, one can see how small Dokdo is. In today’s measurement, the distance between Ulleungdo and Dokdo is 222.3 ri (87.4 kilometers), which is about the same as in the past.
Given that there are many references in historical records that an island is visible far to the southeast of Ulleungdo on clear days, it is obvious that our ancestors were keenly interested in Dokdo.
As mentioned above, the fact that Dokdo is visible from Ulleungdo is important evidence that the two islands are a single entity and Dokdo is our territory. Given that the distance between Ulleungdo and Dokdo is 87.4 kilometers, Dokdo would be visible when the visible distance is favorable. To understand the weather conditions in which one can see Dokdo from Ulleungdo, one needs to understand visible distance.
〈FIG 3〉 The Time when Dokdo’s Best Sunrise May be Seen
The direct factor negatively affecting the visible distance is small particles floating in the air. But local factors such as the degree of atmospheric stability, mixing depth, concentration variations, and synoptic conditions also affect visibility. On the sea, visibility may be reduced due to factors such as fog, rain, and sea fog. Especially in Ulleungdo, July is the month with the highest incidence of fog. There arises a temperature frontal zone in the East Sea as the North Korea Cold Current traveling south from Primorsky Krai encounters the East Korea Warm Current coming from south, which raises the possibility of sea fog in the area. The sea fog observed in the East Sea is affected by the monsoon in the summer months, and is subject more to continental weather conditions than ocean weather conditions.
The relationship between sea fog in the East Sea and visible distance has been confirmed by numerous studies. But there have been few studies on the relationship between sea fog and other weather conditions in Ulleungdo.
This study focuses on what types of weather conditions affect the visible distance in Ulleungdo, and what types of relationships weather conditions such as sea fog and rain have with Dokdo’s visibility from Ulleungdo. In addition to determining ideal weather conditions under which Dokdo is visible from Ulleungdo, we have investigated when the best sunrise scene from Dokdo can be viewed from Ulleungdo (FIG 3).
- [note 133]
- Yi Saek, The Collected Writings of Mogeun (淸明節: “風日淸明 應曆書”).
- [note 134]
- 『高麗史』 (卷五十八, 地理志第十二, 地理/東界/蔚珍縣): “一云 于山 武陵 本二島 相距不遠 風日淸明 則可望見”
- [note 135]
- The Annals of King Sejong Geographical Records (江原道/三陟都護府/蔚珍縣): “于山 武陵二島在縣正東海中(二島相去不遠 風日淸明 則可望見) states, “The two islands of Usan and Mureung are located straight east of the prefecture” (meaning that they are not far apart and one can be seen from the other on a clear day).
- [note 136]
- 『輿地圖書』(江原道/三陟/古跡): “鬱陵島 一云羽陵島 在府東南海中 三峯岌嶪撑空 南峯稍卑 風日淸明 則峯頭樹木 山狼沙渚 歷歷可見.”
- [note 137]
- Visible distance, or visibility, is distance in which one can see an object.
- [note 138]
- Oh Hyeon-sun and Yun Sun-chang (1995), “Characteristics of Air Pollution and Concentration Variations That Affect Visibility,” Korean Society for Atmospheric Environment, pp. 125-129.
- [note 139]
- Seo Jangwon and Lee Hyeon-jeong (2000), “Studies on Sea Fog Characteristics on Waters near Ulleungdo,” Korean Meteorological Society Journal, pp. 258-262; Seo Jangwon, Oh Hwi-jin, An Jung-bae, and Yun Yong-hoon (2003), “Studies on the East Sea’s Fog Prediction System,” Korean Society of Oceangraphy, pp. 121-131.
- [note 140]
- An Jung-bae, Nam Jae-cheol, Seo Jangwon, and Lee Hae-jin (2002), “Sea Fog Prediction Module Development and the Case of Ulleungdo Sea Fog,” Korean Meteorological Society Journal, pp. 155-164.